SingleThreadedSynchronizationContext.cs

public class SingleThreadedSynchronizationContext : SynchronizationContext
{
    private Thread _thread;

    private BlockingCollection<Action> _queue = new BlockingCollection<Action>();

    public SingleThreadedSynchronizationContext()
    {
        _thread = new Thread(() =>
        {
            SynchronizationContext.SetSynchronizationContext(this);

            foreach (var callback in _queue.GetConsumingEnumerable())
            {
                callback();
            }
        });

        _thread.Start();
    }

    public override void Post(SendOrPostCallback d, object state)
    {
        _queue.Add(() => d(state));
    }

    public override void Send(SendOrPostCallback d, object state)
    {
        using (var mutex = new ManualResetEventSlim())
        {
            _queue.Add(() =>
            {
                d(state);
                mutex.Set();
            });

            mutex.Wait();
        }
    }
}